Various articles of manufacture are made with cavities located in areas where mechanical vibration, wind and water can enter, causing undesirable noises and increasing the likelihood that the article will rust. In an automobile, the pillars which outline parts of the windshield and other windows and provide support to the roof have these cavities. Similar cavities are also found in the lower rockers, fenders and quarter panel areas.
These pillars are made from inner and outer sheet metal panels which fit together so that mating flanges are welded in place to form auto body parts. The panel are spaced apart to form a hollow space or cavity between the panels. These voids or cavities generate the undesirable noises and trap moisture therein. Rain, snow, car washes and road moisture splatter on an automobile or truck from normal use. Road moisture is especially undesirable because it often contains rust accelerators such as sodium chloride used to melt ice during colder months where winter is a common occurrence.
Common practice is to fill the cavities with a foam for the purposes of preventing engine vibration, road noise, wind noise and absorbing vibration. Various methods fill the cavities with the foam. For example, foam previously shaped to fit the cavity is inserted through an access opening. Alternatively, a foamable material which is capable of foaming and expanding upon heating is placed in the cavity and later foamed to fill the cavity by heating during paint curing.
The former method of inserting a shaped foam body into a cavity, however, has the problem of not completely filling the cavity. Often, pre-shaped material does not completely fill the cavity from corner to corner. The latter method also suffers from several problems. Heating varies and blowing agents are difficult to measure. Also, where large volumes are filled, cost and added weight are detrimental. These variables also lead to not filling the cavity from corner to corner.
One recent method forms a shaped, heat-expandable sealant plug slightly smaller than the cavity. The process than heats the body member and sealant plug to a predetermined temperature and holds them substantially at that temperature for a predetermined time. The heat expands the sealant plug within the body member cavity and generates an expanded sealant plug which blocks and seals the cavity.
Another recent method uses a sealing material which is disposed in a cavity of a pillar or another member in an automobile and heated for foaming to fill the cavity. The sealing material is nothing more than another urethane foam. This system requires using a process comprising the steps of furnishing a liquid composition comprising an organic polyisocyanate compound, a foam stabilizer and a blowing agent which generates gases at a temperature of about 130.degree. to 210.degree. C., uniformly dispersing an inert gas in the liquid composition by mechanical agitation to form a bubbled composition, shaping the bubbled composition into a predetermined shape and heat curing the bubbled shape at a temperature below the decomposition temperature of said blowing agent.
The more recent methods still have the same problems of the former prior art methods. They still require heating, expansion, predicting volume and have little control over filling out to the corners of the cavities.